Em Wed, Apr 03, 2019 at 12:01:48AM -0700, andrii.nakryiko@xxxxxxxxx escreveu:
> From: Andrii Nakryiko <andriin@xxxxxx>
>
> Current logic in some cases will move bitfield member and then will
> shift all the following members by the size of underlying base type of
> bitfield, which is wrong, as bitfield's size doesn't correspond to the
> size of underlying base type.
>
> Without this fix, reorganizing struct net_device would emit BRAING
> FARTs. Now it doesn't.
>
> Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
> ---
> dwarves_reorganize.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/dwarves_reorganize.c b/dwarves_reorganize.c
> index 9b3aea2..e48d8d5 100644
> --- a/dwarves_reorganize.c
> +++ b/dwarves_reorganize.c
> @@ -321,7 +321,7 @@ static void class__move_member(struct class *class, struct class_member *dest,
> }
> } else if (from_was_last) {
> class->type.size -= from_size + class->padding;
> - } else {
> + } else if (from->bitfield_size == 0) {
> /*
> * See if we are adding a new hole that is bigger than
> * sizeof(long), this may have problems with explicit alignment
After applying this patch I still get a BFA with a vmlinux for x86_64:
[acme@quaco pahole]$ pahole -F btf -C net_device --reorganize vmlinux | tail
struct lock_class_key * qdisc_running_key; /* 2200 8 */
/* size: 2208, cachelines: 35, members: 135 */
/* sum members: 2194, holes: 3, sum holes: 5 */
/* sum bitfield members: 25 bits, bit holes: 4, sum bit holes: 303 bits */
/* paddings: 5, sum paddings: 23 */
/* last cacheline: 32 bytes */
/* BRAIN FART ALERT! 2208 bytes != 2194 (member bytes) + 25 (member bits) + 5 (byte holes) + 303 (bit holes), diff = -256 bits */
}; /* saved 96 bytes and 1 cacheline! */
[acme@quaco pahole]$
[acme@quaco pahole]$ pahole --show_reorg_steps -F dwarf -C net_device --reorganize vmlinux | egrep '^/|BRAIN'
/* bitfield types were fixed */
/* Demoting bitfield ('wol_enabled') from 'unsigned int' to 'unsigned char' */
/* Moving 'min_header_len' from after 'hard_header_len' to after 'irq' */
/* Moving 'hard_header_len' from after 'type' to after 'min_header_len' */
/* Moving 'uc_promisc' from after 'name_assign_type' to after 'min_header_len' */
/* Moving 'dev_port' from after 'dev_id' to after 'type' */
/* Moving 'dev_id' from after 'neigh_priv_len' to after 'dev_port' */
/* Moving 'name_assign_type' from after 'addr_list_lock' to after 'neigh_priv_len' */
/* Moving bitfield('wol_enabled' ... 'wol_enabled') from after 'proto_down' to after 'name_assign_type' */
/* BRAIN FART ALERT! 2240 bytes != 2194 (member bytes) + 25 (member bits) + 40 (byte holes) + 31 (bit holes), diff = -524288 bits */
/* Moving 'needs_free_netdev' from after 'rtnl_link_state' to after 'wol_enabled' */
/* BRAIN FART ALERT! 2248 bytes != 2194 (member bytes) + 25 (member bits) + 43 (byte holes) + 263 (bit holes), diff = -256 bits */
/* Moving 'gso_max_segs' from after 'gso_max_size' to after 'needs_free_netdev' */
/* BRAIN FART ALERT! 2248 bytes != 2194 (member bytes) + 25 (member bits) + 43 (byte holes) + 263 (bit holes), diff = -256 bits */
/* Moving 'proto_down' from after 'qdisc_running_key' to after 'needs_free_netdev' */
/* BRAIN FART ALERT! 2240 bytes != 2194 (member bytes) + 25 (member bits) + 42 (byte holes) + 263 (bit holes), diff = -256 bits */
/* Moving 'watchdog_timeo' from after 'tx_global_lock' to after 'addr_list_lock' */
/* BRAIN FART ALERT! 2232 bytes != 2194 (member bytes) + 25 (member bits) + 34 (byte holes) + 263 (bit holes), diff = -256 bits */
/* Moving bitfield('rtnl_link_state' ... 'rtnl_link_state') from after 'dismantle' to after 'index_hlist' */
/* BRAIN FART ALERT! 2232 bytes != 2194 (member bytes) + 25 (member bits) + 32 (byte holes) + 279 (bit holes), diff = -256 bits */
/* Moving 'dismantle' from after 'reg_state' to after 'rtnl_link_state' */
/* BRAIN FART ALERT! 2232 bytes != 2194 (member bytes) + 25 (member bits) + 29 (byte holes) + 303 (bit holes), diff = -256 bits */
/* Moving bitfield('reg_state' ... 'reg_state') from after 'link_watch_list' to after 'dismantle' */
/* BRAIN FART ALERT! 2232 bytes != 2194 (member bytes) + 25 (member bits) + 29 (byte holes) + 303 (bit holes), diff = -256 bits */
/* Moving 'gso_max_size' from after 'rtnl_link_ops' to after 'reg_state' */
/* BRAIN FART ALERT! 2224 bytes != 2194 (member bytes) + 25 (member bits) + 21 (byte holes) + 303 (bit holes), diff = -256 bits */
/* Moving 'num_tc' from after 'dcbnl_ops' to after 'dismantle' */
/* BRAIN FART ALERT! 2224 bytes != 2194 (member bytes) + 25 (member bits) + 21 (byte holes) + 303 (bit holes), diff = -256 bits */
/* Moving 'dcbnl_ops' from after 'rtnl_link_ops' to after 'gso_max_size' */
/* BRAIN FART ALERT! 2216 bytes != 2194 (member bytes) + 25 (member bits) + 13 (byte holes) + 303 (bit holes), diff = -256 bits */
/* Moving 'rtnl_link_ops' from after 'sysfs_rx_queue_group' to after 'link_watch_list' */
/* BRAIN FART ALERT! 2208 bytes != 2194 (member bytes) + 25 (member bits) + 5 (byte holes) + 303 (bit holes), diff = -256 bits */
/* Final reorganized struct: */
/* BRAIN FART ALERT! 2208 bytes != 2194 (member bytes) + 25 (member bits) + 5 (byte holes) + 303 (bit holes), diff = -256 bits */
[acme@quaco pahole]$
- Arnaldo
